Engine cranks but wont start?

[EDIRTYBASTARD]

Hey rev,
Here's the deal, I bought a 1991 318is cranks and won't start, the guy I bought it off of replaced the crank sensor and cam sensor also the fuel pump..*note* fuel pump doesn't prime when key is turned..

Here's a list of things I did:
Tested all power and grounds on the engine harness back to the ecu
Checked relays and fuses

I'm thinking it could possibly be the crank sensor, ignition coil or ecu..

Any input or diagnostic ideas would be greatly appreciated!!

[jlevie]

The first check would be to find out if you have spark and normal pressure in the fuel rail when cranking the engine. No spark and no operation of the fuel pump when cranking the engine could be:

No timing reference data to the DME (CPS)
No power to the DME (Main relay, fusible link, ignition switch)
Bad DME

[EDIRTYBASTARD]

I checked all fuses, relays, and power through the whole harness. I checked for spark using a screw driver through the spark plug to gap to the strut tower. *got nothing* However I didnt check fuel pressure, and i im pretty sure im getting nothing cuz the fuel pump wasnt priming until we jumped it..

[jlevie]

If the DME and coil are getting power, but there's no spark, the problem with be with the CPS or DME. The pump is controlled by the DME and only runs when the DME sees timing data from a rotating engine. So if you don't have spark the pump is probably not running.

[EDIRTYBASTARD]

Whats the DME. I know (CPS)

[jlevie]

The DME (Digital Motor Electronics) is the engine computer.

[EDIRTYBASTARD]

Ahh.. Yea I call it the ECU. lol, But anyway I think thats a good possibility that its toast. How would I check the crank sensor. My friend from barvarian motor sports says to crank it and if the CEL stays on then its most likely the CPS.

[Danny]

Ahh.. Yea I call it the ECU. lol, But anyway I think thats a good possibility that its toast. How would I check the crank sensor. My friend from barvarian motor sports says to crank it and if the CEL stays on then its most likely the CPS.

Check the resistance of it (Ohms)

[b*saint]

Everyone calls it an ECU except Bosch users.

[EDIRTYBASTARD]

My ECU is Bosch ^_^ haha. Im probably gonna check the Crank Sensor In a few min.

[b*saint]

How are you going to check it? You have a scope?

[EDIRTYBASTARD]

I have a multi-meter if your talking about checking the resistance.

[b*saint]

OOOOO I see. I thought you were going to check if it was outputting correctly.

[EDIRTYBASTARD]

How would I test if its out putting correctly?

[jlevie]

How would I test if its out putting correctly?

With an oscilloscope